The positively charged part at the centre of an atom is called as:

Correct answer: (d) Nucleus

Explanation

The nucleus is the small, dense, positively charged core of an atom, discovered by Rutherford in his gold-foil experiment (1911).

It holds the protons (positive) and neutrons (neutral), together called nucleons, so its overall charge is positive. A proton is a particle inside the nucleus, not the central part itself.